1. Field of the Invention
The invention relates to a connector switch apparatus which can provide a signal from either of two sources. More particularly, the invention relates to a connector switch apparatus which can provide either a satellite or cable television signal or a ghost-free off-air television signal to a television or a television monitor (either hereinafter referred to as a "television").
2. Description of Related Art
With the development of cable and satellite television transmission, television viewers are shying away from receiving television signals, by means of a conventional antenna, from off-air television transmission. (Such a television signal is hereinafter referred to as an "off-air television signal".) Rather, television viewers are more and more often opting to receive television signals from cable or satellite television transmission. (Such a television signal is hereinafter referred to as a "satellite or cable television signal".) Two inter-related reasons for this are:
(a) television viewers do not want to have to manipulate a conventional television antenna which receives off-air television signals (e.g., a television viewer may need to physically adjust that antenna or its phase) so that better quality television images can be obtained therefrom, especially when no similar manipulation is required with respect to cable or satellite television signals to obtain good quality television images; and
(b) the television images which have been obtained from television signals received via a conventional television antenna from off-air television transmission have not had as good a quality, because of ghosting, as those which have been obtained from television signals received from cable or satellite television transmission.
A problem or potential problem of cable and satellite television transmission is that they currently do not (such as in the case of DSS Satellite Television Systems) or may not now or in the future (such as in the case of cable television) transmit, in some or all markets, certain local programming which is transmitted via off-air television transmission and can be received by a television viewer by means of a conventional television antenna. As a result, in such markets, the only way in which a television viewer can obtain such local programming is by hooking up his or her television to a conventional television antenna. Because conventional televisions typically have only one television signal (i.e., R/F) input, a television viewer in such a market who wishes to have the ability to receive both cable or satellite television and such local programming cannot do so without additional equipment, unless he or she continuously connects and disconnects the R/F input to (a) (i) a cable box or the cable directly or (ii) a satellite antenna and tuner and (b) a conventional television antenna.
An existing solution to this problem is a conventional A/B switch, i.e., connecting the R/F input of a television to the output of the switch, and the inputs of the switch to a cable or satellite television tuner and a conventional television antenna, respectively. However, that solution does not solve either of the following two problems, mentioned above:
(a) a television viewer will still have to manipulate a conventional television antenna to obtain better quality television images from off-air television signals; and
(b) the television images which a television viewer obtains from off-air television signals, by means of a conventional television antenna, will not be as good as those obtained from cable or satellite television signals, because of ghosting.
With respect to the latter, it is noted that the development of baseband ghost cancellation, described generally by W. Ciciora et al. in "A Tutorial On Ghost Cancelling in Television Systems", IEEE Trans. on Consumer Elec., Vol. CE-25, No. 1, pp 9-44 (February 1979), which is incorporated herein by reference, reduces the effects of ghosting on, thereby improving the quality of, the television images which are obtained from off-air television signals. (Methods and apparatus illustrating preferred methods of baseband ghost cancellation are described in U.S. Pat. Nos. 5,047,859, 5,111,298, 5,121,211, and 5,172,232, which are all incorporated herein by reference.) Nevertheless, the ability of baseband ghost cancellation to perform ghost cancellation, and the quantity of such ghost cancellation when it can be performed, is limited by the reception quality of a television signal received by a television. Accordingly, if the television signal which is received by a television and supplied to a baseband ghost cancellation unit is of poor reception quality, the baseband ghost cancellation unit may either not be able to perform ghost cancellation on that signal, or if it can perform ghost cancellation, not be able to perform sufficient ghost cancellation to produce a television signal from which substantially ghost-free images can be obtained. (That type of television signal is hereinafter referred to as a "ghost-free television signal".)